<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Onload</title>
</head>
<body>
    <script>
       
        window.onload = function (param) {  
                dis.onclick = function(){
                    alert('a~a~a');
                }
        };
        </script>


</body>
<button id="dis">fuck me!</button>
</html>